Photographic developers



PHOTOGRAPHIC DEVELOPERS George Schwarz, Glen Head, N. Y., assignor to Powers Chernco, Inc., Glen Cove, N. Y., a corporation of New York No Drawing. Application September 7, H55

Serial No. 533,010 3 Claims. (CI. 96-66) The present invention relates to novel and improved photographic developers.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the steps, process and compositions and improvements herein shown and described.

Photographic developers, especially those having a relatively low concentration of sulfite ions have very poor keeping qualities and are subject to rapid oxidation when exposed to the atmosphere. Under certain unfavorable conditions even high sulfite concentrations in developers do not prevent rapid aerial oxidation, for example when the water contained in the developer is contaminated with very small amounts of iron, copper, or other heavy-metal containing ionic compounds, and in normal practice it is diflicult and seldom feasible to provide for water fre of such heavy-metal ionic compounds.

Developers are also subject to other types of deterioration, particularly in deep tanks, such as are used for the,

commercial processing of roll film. Often such developers are subjected to deterioration by micro-organisms which reduce the sulfite tosulfide and causeputrefractionv of the developer and fogging of the film. Most photographic developers also react with the impuritiesin the water to form precipitates of calcium and magnesium salts and cause the formation of cloudy solutions, which can be avoided only by the use of specially purified Water which is not generally available for the purpose.

The present invention has for its object the provision of a photographic developer which has superior keeping qualities, is not readily susceptible to aerial oxidation, and which does not suffer from the use of the ordinary water which is generally available for the preparation of such a developer. A further object of the invention is the provision of a developer which is not readily susceptible to putrefaction and which, in use, reduces the fogging which often occurs in the commercial use of conventional developers. Still another object is the provision of a developer which does not seriously suffer from being made up with relatively hard water, or water containing normal amounts of copper, iron or other heavy-metal ionic compounds.

The various disadvantages of the conventional developers, as set forth above, can be greatly reduced and largely avoided by the addition to the conventional photographic developer of relatively small amounts of an organic cyclic compound which is water-soluble and contains the atomic grouping OH O =t t in a quantity of from about 0.01 to about 0.25 mol per litre of developer, preferably about 0.1 mol per litre, although the amount of such cyclic compound may be varied widely within the limits given. Preferably, the water soluble salts of kojic acid or the acid itself is used, in quantities of from about 2 grams to as much as 30' or 35 grams per litre, the pH of the developer being adjusted as desired in view of the .quantity of kojic acid or kojic acid salt used, so that the alkalinity (or acidity) of the developer is substantially the same as would be used with a conventional developer.

The kojic acid and its related compounds are to be distinguished from the compounds related'to ascorbic acid which do not contain the -pyrone grouping, although they do contain the l group. more expensive than those which contain. both the 'ypyrone group and the above-mentioned functional group, such as kojic acid.

It will be understood that the foregoing general description and thefollowing detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

.The following are specific examples. of variouspreferred photographic developers in accordance; with the present invention and which illustrate the principles of the invention.

Example 1.Met0l-hydr0quin0ne developer If the water is relatively hard, the kojic acid is prefer-j ably dissolved in the water before the remainder of the developer is dissolved in the water, thereby avoiding the formation of 'a calcium or magnesiumprecipitate.

Whether or not the kojic acid is first dissolved in the water, the developer is protected against reduction of the sulfite to sulfide by micro-organisms which contaminate the water.

Example 2.Tanning developer A tanning developer with a low sulfite concentration, which can be omitted for certain purposes, if desired, has its tray life doubled or trippled with respect to a similar developer which does not include the addition of the kojic acid. Such a developer comprises:

Grams Oatechol 5 Sodium sulfite (optional) 3 Potassium carbonate"; 30 Kojic acid 10 Water, q. s. ad. 1 litre.

The sodium sulfite may be omitted, decreased or increased, if desired, and the catechol may be partially or completely replaced by pyrogallol or hydroquinone. The kojic acid may be varied from 2 grams to as much as 30 or 55 grams, although when higher amounts of kojic acid are used, it may be desirable to increase slightly the amount of alkali so as to maintain the pH within the desired limits.

Example 3.-Alkali-free (amidol) developer An alkali free developer can be made with amidol which has a tray life approximately double that of a similar developer not including the kojic acid.

Grams Amidol 5 Sodium sulfite 50 Kojic acid 15 Water, q. s. ad. 1 litre.

Such compounds are much less effective and Example 4.--Extreme contrast (lithographic) developer Grams Sodium formaldehyde-bisulfite 40 Hydroquinone 25 Kojic acid 10 Sodium carbonate 38 Potassium bromide 2 Water, q. 5. ad. 1 litre.

Such a developer has a greatly improved tray life over a similar developer prepared'without kojic acid, as well as with respect to a similar developer in which the pH was made equivalent by the addition of boric acid in place of the kojic acid. The kojic acid not only serves to maintain the strength of the developer over a longer period of time, but also minimizes the discoloration of the developer. The kojic acid concentration is not critical and may be varied from 1 gram to 25 grams per litre if the acidity is properly adjusted by using more or less of the sodium carbonate, or otherwise.

Example 5.-Clor-c0upling developer Wt A color-coupling developer with increased resistance against aerial oxidation and color fog may be prepared as follows:

Grams Paradimethylaminoaniline hydrochloride 10 Sodium sulfite 5 Sodium carbonate 35 Kojic acid a-Naphthol 5 r r r 4 the chemicals, such as the alkaline salt, e. g. sodium carbonate. It is of little importance in which group the potassium bromide is included, but it is always advantageous to have the developing agent in the same package with the sulfite.

Thus, the developer of Example 1 would preferably be packaged dry as a first package comprising the monomethylparaminophenol sulfate, sodium sulfite and kojic acid, while the second package would comprise the sodium carbonate, hydroquinone and potassium bromide. Likewise, the developer of Example 2 would preferably have the second package include only the potassium carbonate, with the remainder of the ingredients in the first package;

The quantity of water given in all of the above formulae is the preferable quantity, and of course, it may be widely varied in accordance with standard photographic techniques, depending upon the efiect desired from the developer.

The invention in its broader aspects is not limited to the specific steps, process and compositions shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A photographic developer comprising an organic silver-halide developing agent, an alkali sulfite and an amount sufiicient to form from 1 to 35 grams per liter when dissolved in water of a compound selected from this group consisting of kojic acid and its water soluble sa ts.

2. A photographic developer as claimed in claim 1 in which the alkali is sodium formaldehyde bisulfiteand the developing agent is hydroquinone.

3. A photographic developer as claimed in claim 2 in which the compound is kojic acid.

References Cited in the file of this patent Pontius: PSA Journal, Section B, September 1951, pp. 76-79. 

1. A PHOTOGRAPHIC DEVELOPER COMPRISING AN ORGANIC SILVER-HALIDE DEVELOPING AGENT, AN ALKALI SULFITE AND AN AMOUNT SUFFICIENT TO FORM FROM 1 TO 35 GRAMS PER LITER WHEN DISSOLVED IN WATER OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF KOJIC ACID AND ITS WATER SOLUBLE SALTS. 